On the other hand, replacing YouTube as a hosting platform isn't too hard (I think? I don't actually have much experience with this but there are alternatives).
Of course the big issue isn't YouTube the host, it's YouTube the marketing platform - but even here there are alternatives. Host on vimeo, but use other social media more. More Facebook posts. Get an audience via podcasts. I'm not saying it's easy, I'm saying that I'm not at all convinced that YouTube really is a monopoly in the sense where we want to do something about it.
It's very easy to view a video elsewhere than YouTube.
It's difficult to convince other people to view a video elsewhere than YouTube. You'd have to be on YouTube to begin with to reach them. Sure, there are Facebook and Twitter. But if you want to get off those as well (and I do)… good luck.
If you live in a remote city with one wallmart and no other stores, and wallmart bans you, that's a problem.
Yes, there are alternatives, but 97% of the market is definitely a monopoly.